Manufacture of gold alloys



Patented Oct. 1, 1940 MANUFACTURE OF GOLD ALLOYS Otto Loebich, Pforzheim, Germany, assignor, by mesne assignments, to Chemical Marketing I Company Inc., New York, N. Y.

No Drawing. Application February 11, 1939, Seligals No. 255,978. In 'Germany February 2,

2 Claims.

My invention relates to the manufacture of gold alloys with a content of gold below 50%.

The hitherto known alloys with a content of gold less than 50% containing besides gold a certain amount of copper, silver and zinc either alone or together, have not proved satisfactory I especially with respect to the resistance against tarnishing than the hitherto known alloys with the same or similar contents of gold. Moreover, these new alloys-may easily be adapted to the desired requirements with respect to the color of gold or some other qualities.

According to my invention the composition layer whilst an alloy according to my'invention with 33.3% gold, 45% copper, 18.7% zinc and 3% palladium will only be affected to a minor extent.

The fusion points of the above mentioned palladium free alloys and those of the respective alloys which'contain palladium are substantially the same. However, the alloys containing palladium show a somewhat increased hardness.

The qualities of the above mentioned alloys containing gold, copper, zinc, palladium and/or platinum may also be affected advantageously by the presence of silver. The quantity of the silver content may amount to 28%, preferably 5 to 25%, calculated on the total alloy.

An alloy with 41.7% gold, 33.3% copper, 10.0% zinc, 8.0% palladium and 7.0% silver with a yellow-reddish color, does not substantially tarnish in sulphuric solutions.

Furthermore, the qualities of the alloys may for instance be influenced by the addition of silver. in such a way that the hardness may be increased considerably without deteriorating the resistance against tarnishing. For instance, the addition of silver may increase the hardness of the alloys 0 of the gold alloys may be as follows: in soft annealed condition from about 55 to about 25 25 to 50%, preferably 30 to 45% gold, to 55, 70 kgrs/mm. average. Alloys with higher conpreferably to 50% copper, 3 to prefertents of silver, for instance 20%, possess an averably 5 to 20% zinc and 1 to 10%, preferably age hardness of about 115 kgrs./mm. in soft 2 to 8% palladium and/or platinum. annealed condition. Besides, those alloys may be With alloys of the above mentioned coinpositempered which may prove advantageous for cer- 30 tion the platinum metals efiect an improvement taln purposes. on the resistance against tarnishing. The following table shows a summary of silver An alloy, containing 33.3% of gold, 58% copfree and silver containing alloys with statement per and 8.7% zinc and having a red color, for of hardness and fusion'point.

Pd An Cu Zn Ag Color Hardness ggf fl .Kgm/mm. C'. 3.0 33.3 33 8.7 53 33030040 3.0 33.3 45 13.7 54 020mm 3.0 37.5 39.5 10.0 104 ,90030340 3.0 37.5 27 13.5 117 31030710 3.0 33.3 37 18.7 37 33530300 3 33.3 37.0 3.7 113 33030740 3.0 33.3 32.0 13.7 122 34030715 7 instance, tarnishes in sulphur containing solu- In carrying out my invention the alloys may tions with the formation of a black layer. If contain other metals to a lesser degree besides the 3% copper have been replaced by 3% palthe above mentioned components. These are, for ladium, the alloy which now contains 33.3% gold, instance, aluminium, magnesium, nickel, iron, 55% copper, 8.7% zinc and 3.0% palladium will antimony, tin, cadmium.. The alloys may cononly be slightly changed by the same sulphuric tain up to Of those addition metals, solution. culated on the total alloy. The addition of those A gold alloy, of yellow color with 33.3% gold, metals may influence the qualities of the alloys 48% copper and 18% zinc tarnishes in a sulphuric considerably and make them adapted for the solution with the formation of a dark brown desired requirements. By the addition of iron and nickel the alloys mam-for instance, be hardened. By the addition of, for instance, tin, antimony and cadmium the resistance against tarnishing may be improved. Aluminium and magnesium increase the hardness as well as improve the resistance against tarnishing. l

The following table shows a number of alloys which contain those metals of addition:

special advantages, as the perhaps occurring dimculties decrease by enhancing the fineness of the grain of the alloy.

'It has proved advantageous to add the grain refining additions in the form of preliminary alloys with base metals, such as for instance tin, cadmium and the like. In this case preferably such base metals are used for the manufacture Pd Au Cu Zn Ag Color Hardness Average fusion point .l'i'gnnhn'm. C'. 3. 0 33. 3 32. 0 13. 7 17 1 Mi? Yellow 120 820 C0 690 3. 0 33. 3 32. 0 13. 7 16 :2 C d 114 830 to 690 3. 0 33. 3 27. 0 8. 7 26 2 A] d0... 151 790 to 710 3. 0 33. 3 27. 0 8. 7 26 2 F6 RflddlSh-YQHOW. 153 825 T0 740 3. 0 33. 3 45. 0 8. 7 8 2 Al -.dO 88 910 m 820 3.0 33.3 45.0 8.7 8 2N1 Red 82 940M860 structure. As some of the alloys made accord-.

ing to my invention as a consequence to the broad fusion intervals tend to liquate the supplemental use of grain refining additions has of the preliminary alloys which form a predestined part of the resulting alloy.

What I claim is:

1. Gold alloy consisting of to 50% gold, 15 to 55% copper, 3 to zinc, 1 to 10% of a metal selected from the group consisting of palladium and platinum and an addition up to 25% silver. 2. Gold alloy consisting of 30 to gold, 25 to copper, 5 to 20% zinc, 2 to 8% of a metal selected from the group consisting of palladium and platinum, about 25% silver.

- O'I'IO LOEBICH. 

